I gave a lecture not long ago in London in which I asserted with a flourish that Wordsworth killed off Romantic biography. At the end of the session I was rebuked by a dear friend, who pointed out that I never seemed to pass up the opportunity to be rude about Wordsworth, and that what I had said on this occasion was ignorant and untrue.

Well, I had overstated the case. Wordsworth (as I mentioned recently in these pages) was an articulate enemy of frank biography. He attacked an indiscreet life of Burns, encouraged the suppression of Crabbe's letters, and crucially influenced the first biography of Keats. But he was not alone. Coleridge was of the same party, and articulated his position some years before Wordsworth did. Wordsworth's "Letter to a Friend of Burns" is dated 1816. Coleridge's "Prefatory Observation on Modern Biography" appeared in The Friend in 1810.

It is in this essay that Coleridge called the age he was living in "emphatically the age of personality" - and so indeed its great writers appear to us. They are great personalities, and that is how they come across in, for instance, the essays of Hazlitt. But some of them at least seem to have suffered an intense queasiness about the way they were going to be viewed, if biography was to take its cue from Boswell, and show them in intimate detail.

"An inquisitiveness into the minutest circumstances and casual sayings of eminent contemporaries, is indeed quite natural," writes Coleridge, in his worst moralising vein; "but so are all our follies, and the more natural they are, the more caution we should exert in guarding against them. To scribble Trifles even on the perishable glass of an Inn window, is the mark of an Idler; but to engrave them on the Marble Monument, sacred to the memory of the departed Great, is something worse than Idleness." A genuine biography should be distinguished by "the firmness with which it withstands the cravings of worthless curiosity, as distinguished from the thirst after useful knowledge". For "the great end of Biography" is "to fix the attention and to interest the feelings of men, on those qualities and actions which have made a particular Life worthy of being recorded".

Biographical facts should have a certain dignity, just as in the 18th century there was a view that history itself should preserve its proper dignity. Preserving the "dignity of history" meant the conscious suppression of trivial or circumstantial details, as being "matter of inferior grade and texture". This view was apparently articulated by the Scottish historian William Robertson. It is the opposite of that favoured by both Johnson and Boswell. But it is a view of great antiquity. It was challengingly epitomised by another Scot, Sir James Mackintosh: "A life which is worth reading ought never to have been written."

The point of bringing this up is to show that it was not Victorian morality that made the frank biography impossible. It was a strain of thought, a line of debate, stretching back to the 18th century and beyond. It was an issue at the heart of Romanticism, for it was thought that knowledge of a man's shortcomings would taint or even destroy the reader's admiration of his art.

But even if the trivial facts recorded by the biographer were in no way to the discredit of his subject, the notion of the dignity of history would prevent their being set down. We find this principle nobly expressed in the dedication of John Toland's life of Milton. "I shall not be too minute in relating the ordinary circumstances of [Milton's] Life," writes Toland, "and which are common to him with all other Men. Writings of this nature should in my opinion be design'd to recommend Virtue, and to expose Vice; or to illustrate History and to preserve the memory of extraordinary things. That a Man, for example, was sick at such a time, or well at another, should never be mention'd; except in the Causes or Effects, Cure or Continuance, there happens something remarkable, and for the benefit of Mankind to know. I had not therefore related Milton's Headachs in his Youth, were it not for the influence which this Indisposition had afterwards on his Eys, and that his Blindness was rashly imputed by his Enemies to the avenging Judgment of God."

Today we implore the biographers of the past, give us Milton with his headaches, give us the chilblains, tell us everything, everything you can recall. But to them it would have seemed a betrayal, or at best a professional shortcoming, to burden their account with irrelevant minutiae. What mattered were the achievements and the virtues. We would say: what mattered was the Big Picture.